1. Statement of the Technical Field
The present invention relates to the field of geographic information systems (GIS) technology and more particular to the three-dimensional visualization and analysis of geographic data.
2. Description of the Related Art
Traditional maps represent abstractions of real world locations. Specifically, traditional maps are based upon discrete samples of location-based elements. The discrete samples can be applied to two-dimensional print to provide a visual representation of a real world location, whether symbolically, illustratively, or otherwise. End-users who use maps interpret the two-dimensional visual representation to facilitate a geographical analysis. Still, as the comfortable reach of the two-dimensional map can suffice for many applications, to model reality most clearly, a three-dimensional (3D) map can prove most advantageous.
GIS technology includes computer systems configured to assemble, store, manipulate and display geographically referenced information. Most conventional GIS technologies process data identified according to two-dimensional spatial references. Still, conventional GIS technologies can be configured to process topographic data, in addition to rudimentary two-dimensional data, usually in the form of a digital elevation model. Based upon the topographic data, isometric views and contour maps can be generated. GIS users, however, have recognized the limitations of a two-dimensional modeling paradigm for modeling 3D phenomena, even when combined with topographic data.
Notably, some GIS technologies can integrate scene generation systems for the 3D visualization of data. Yet, although z-axis coordinate data now can be easily recorded or can be made readily available for the visualization of surface features, this 3D aspect of GIS data historically has been disregarded in conventional GIS software. Rather, in conventional GIS technologies, z-axis coordinate data has been included only to “drape” a two-dimensional mapping over topographic data to produce what is known as a 2.5D model. Still, the use of a 2.5D model ought not to be confused with 3D GIS. Rather, to be properly characterized as a 3D GIS, GIS technology must be able to handle geographic data as a volumetric object rather than as merely a two-dimensional surface.
Presently, fully functional 3D, volumetric GIS technologies do not exist. In fact, most conventional GIS technologies permit end-users to locate objects given only two-dimensional geo-spatial coordinates. In particular, database systems have been developed in which two-dimensional spatial structures can be created, stored and managed. Examples of two-dimensional geo-spatial coordinates include an address, points on a map, and a latitude/longitude pair. Based upon these stored two-dimensional spatial structures, 3D visualization technologies are able to create and visualize 3D structures and sequences.
For example, U.S. Pat. No. 6,161,105 issued to Oracle Corporation on Dec. 12, 2000 (the “'105 patent”) discloses one such database engine in which binary helical hyperspatial (HH) codes are used to represent multi-dimensional data in a relational database. In particular, the invention disclosed in the '105 patent supports three geometric primitive types and geometries formed from the primitive types. The three geometric primitive types are Point, Line String, and N-point Polygon. Importantly, however, each of the three geometric primitive types are defined merely in two dimensions. In particular, as explicitly stated in column 7, lines 39-44 of the '105 patent, “[T]he present invention's BH code data structure is modeled . . . in two dimensions . . . as a quad tree structure derviced using recursive decomposition.” Accordingly, the database engine of the '105 patent cannot support pure, 3D volumetric geo-spatial queries.
Thus, the combination of database technologies with 3D visualization technologies cannot support purely 3D, volumetric, geo-spatial querying. In that regard, stored two-dimensional spatial structures and 3D visualization technologies cannot be combined to locate points, lines or objects which intersect a volume. Similarly, the combination of stored two-dimensional spatial structures and 3D visualization technologies cannot be used to identify objects which exist within other 3D objects. Hence, the remains a need for a system which can support purely 3D, volumetric, geo-spatial querying.